The present invention relates to a liquid jetting device, and in particular, to a liquid jetting device wherein a liquid is jetted from a liquid jetting section, and a jetted trace of the liquid is recorded on a recording medium such as paper, cloth, nonwoven fabric and a plastic film, as, for example, in an ink jet printer.
In the case of an ink jet printer used for cloth, for example, a drop of ink (liquid) is jetted from a nozzle of a liquid jetting section, namely, of a print head onto a web (recording medium) on a platen so as to print a pattern. In the case of a color print, a print head has thereon ink heads which are respectively for the four primary colors of cyan, magenta, yellow and black, for example, and a combination of ink dots jetted from various ink heads expresses various colors and patterns. Combinations of colors of ink dots and patterns formed by them are specified by image forming data supplied from the control unit (computer). Density of ink dots constituting a pattern is usually between several hundred dpi to more than one thousand dpi.
Ink is supplied to a print head directly from an ink tank or through an ink tube. When letting ink run through a path from the ink tank to the print head initially, a pressure difference which makes the pressure on the part of the ink tank to be higher relatively than that on the part of the tip of the print head is given between the ink tank and the tip of the print head, to feed ink forcibly. The pressure is generated by suction or pressurization caused by a pump. Even when a nozzle of a print head is clogged with foreign substances such as dust or air bubbles, the foreign substances are ejected out of the nozzle together with ink by force feeding. The force feeding of ink of this kind for ejection of foreign substances is also conducted under the pressure which is the same as that in initial ink running.
When the pressure which is the same as that in initial ink running is used in force feeding of ink for ejection of foreign substances, air bubbles have failed to be ejected out sufficiently, depending on their size and location, which has been a problem.
To be concrete, an air bubble which is produced in an ink tube and is relatively large is easily fed forcibly by a high pressure, but when it fragments into small air bubbles, they are hardly moved. When such air bubbles are deposited in an ink manifold of an ink head, they affect ink jet operations, while when air bubbles which are further smaller are stuck to an inner wall of a jetting channel (nozzle) of the ink head, the jetting direction of ink loses its accuracy.
The diameter of the nozzles of the print heads capable of making a print having such a high dot density mentioned above is extremely small, and jetting failure caused by adhesion of dyes or pigments of the ink tends to occur, requiring cleaning of the print head on a timely basis.
As an example of a conventional liquid jetting device equipped with a cleaning unit for the print heads, there is described a device in TOKKAIHEI 4-185450, for example. In this device, a cleaning roller made of porous material is brought into contact with a print head, and thereby smudges on the nozzle plane are absorbed when the cleaning roller is rotated on the nozzle plane by travel of the print head.
Further, as another example of a conventional liquid jetting device equipped with a cleaning unit for a print head, there is described, for example, a device in TOKKAIHEI 6-079880. In this device, a cleaning blade made of porous material is caused to hold a cleaning liquid and is brought into contact with the print head, so that the front surface of the print head is wiped by the cleaning blade as the print head travels along its limited path.
In the aforesaid example of the conventional jetting device, the print head is brought into contact with a cleaning roller or a cleaning blade whose position is fixed so as to clean the ink jetting plane by utilizing sucking action or wiping action based on traveling of the print head. However, the traveling speed of the print head is the same as the main scanning speed in the course of printing, or it can not be changed greatly even if it is changed. Therefore, the desired cleaning needs to be conducted within a given range of traveling speed, requiring hard work in selection of materials and shapes of a cleaning roller or the cleaning blade, or in selection of the cleaning liquid, which has been a problem.
In particular, in the conventional device described in TOKKAIHEI 4-185450, the cleaning effect is insufficient because smudges stuck on the nozzle plane can not be scraped off, though smudges on the nozzle plane can be absorbed, due to utilization of rotations of a cleaning roller on the print head surface. In the conventional device described in TOKKAIHEI 6-079880, on the other hand, a mechanism for supplying a cleaning liquid and a mechanism for absorbing smudges are complicated, and sufficient effect of cleaning is not always obtained, because the same contact surface of the cleaning blade is always used.
The present invention has been achieved to solve the problems mentioned above, and its object is to materialize a liquid jetting device wherein foreign substances and air bubbles contained in a liquid are appropriately removed and a liquid jetting section is cleaned appropriately.
The object stated above can be attained by the following structures.
(A) A liquid jetting apparatus, comprises
a head provided with a liquid jetting section;
a feeding means for feeding a liquid to the head;
a control section for controlling the liquid jetting section to jet the liquid such that a jetting trace of the liquid is recorded on a recording medium; and
a liquid ejecting means for varying a pressure in the head by plural steps so as to eject the liquid in the head from the liquid jetting section.
Here, as the liquid ejecting means for varying a pressure in the head in plural steps so as to eject the liquid in the head from the liquid jetting section, it may be permissible to be able to merely vary the pressure in the head by plural steps. The liquid ejecting means includes a case that the pressure steps in the head are changed differently in accordance with an objective of liquid ejection, the property of foreign material, and the kind of liquid and a case the pressure is varied by plural pressure steps by only a single ejecting action.
(B) A liquid jetting apparatus, comprises:
a head provided with a liquid jetting section;
a feeding means for feeding a liquid to the head;
a control means for controlling the liquid jetting section to jet the liquid such that a jetting trace of the liquid is recorded on a recording medium;
a wiping means for wiping the liquid jetting section of the head, the wiping section being rotatable and having an outer peripheral surface at least on which a wiping member having a liquid-absorbing characteristic is provided;
a driving means for rotating the wiping means; and
a cleaning liquid feeding means for feeding a cleaning liquid to the wiping means.
Further, the object stated above can be attained by the following structures as a preferable embodiment. (Item 1) A liquid jetting device to jet a liquid from a liquid jetting section and to record a jetted trace of the liquid on a recording medium, wherein there is provided a liquid ejecting means in which the pressure is varied in plural steps to eject the liquid from the liquid jetting section.
In the invention of Item 1, the liquid ejecting means can conduct liquid ejection which is in conformity with properties of foreign substances, by varying the pressure in plural steps. Incidentally, air bubbles are included in the category of foreign substances. (Item 2) The liquid jetting device described in Item 1, wherein the liquid ejecting means stated above is provided with a pressure releasing means.
In the invention of Item 2, the pressure releasing means gives the time constant for increase or decrease of pressure. (Item 3) The liquid jetting device described in Item 2, wherein a pressure releasing gateway of the pressure releasing means can be opened and closed.
In the invention of Item 3, the pressure releasing means opens or closes the pressure releasing gateway to adjust the time constant. (Item 4) The liquid jetting device described in either one of Item 1-Item 3, wherein the pressure is varied in at least two steps in the liquid ejecting means.
In the invention of Item 4, the liquid ejecting means conducts liquid ejection which is in conformity with properties of foreign substances, by varying the pressure in two steps. Incidentally, air bubbles are included in the category of foreign substances. (Item 5) The liquid jetting device described in Item 4, wherein the pressure is varied in three steps in the liquid ejecting means.
In the invention of Item 5, the liquid ejecting means conducts liquid ejection which is in conformity with properties of foreign substances, by varying the pressure in three steps. (Item 6) The liquid jetting device described in Item 5, wherein the relatively high pressure is used by the liquid ejecting means when it conducts initial running of the liquid for the liquid jetting section and/or unclogging of the liquid jetting section, the relatively low pressure is used by the liquid ejecting means when it removes air bubbles in the liquid manifold of the liquid jetting section, and the relatively lower pressure is used by the liquid ejecting means when it removes air bubbles in the jetting channel of the liquid jetting section.
In the invention of Item 6, the liquid ejecting means uses pressures in three steps each in its proper way, for initial running of a liquid and/or unclogging of the liquid jetting section, removing air bubbles in the liquid manifold and for removing air bubbles in the jetting channel. (Item 7) The liquid jetting device described in either one of Item 1-Item 6, wherein the pressures in plural steps are generated by intermittent operations of a pump in the liquid ejecting means.
In the invention of Item 7, the liquid ejecting means adjusts the pressure by means of a pulse width of intermittent operations of a pump. (Item 8) The liquid jetting device described in either one of Item 1-Item 6, wherein the pressures in plural steps are generated by intermittent operations of a pump in the liquid ejecting means.
In the invention of Item 8, the liquid ejecting means adjusts the pressure through the speed of a continuous operation of a pump. (Item 9) The liquid jetting device described in either one of Item 1-Item 6, wherein the liquid ejecting means generates the relatively high pressure through intermittent operations of a pump and generates the relatively low pressure through a continuous operation of a pump.
In the invention of Item 9, the liquid ejecting means adjusts the relatively high pressure by means of a pulse width of intermittent operations of a pump and adjusts the relatively low pressure by means of the speed of a continuous operation of a pump. (Item 10) The liquid jetting device described in either one of Item 1-Item 6, wherein the liquid ejecting means generates the relatively high pressure through a continuous operation of a pump and generates the relatively low pressure through intermittent operations of a pump.
In the invention of Item 10, the liquid ejecting means adjusts the relatively high pressure by means of the speed of a continuous operation of a pump and adjusts the relatively low pressure by means of a pulse width of intermittent operations of a pump. (Item 11) The liquid jetting device described in either one of Item 1-Item 10, wherein the liquid ejecting means generates pressures in plural steps through suction.
In the invention of Item 11, the liquid ejecting means imposes pressures in plural steps on a liquid. (Item 12) The liquid jetting device described in either one of Item 1-Item 10, wherein the liquid ejecting means generates pressures in plural steps through pressurization.
In the invention of Item 12, the liquid ejecting means imposes pressures in plural steps on a liquid through pressurization. (Item 13) A liquid jetting device to jet a liquid from a liquid jetting section and to record a jetted trace of the liquid onto a recording medium, wherein there are provided a wiping means which wipes the liquid jetting section with an outer circumferential surface of its cylindrical wiping member that has a liquid-impregnating characteristic and rotates and a cleaning liquid supplying means which supplies a cleaning liquid to the wiping means mentioned above.
In the invention of Item 13, a cleaning liquid impregnated wiping means is rotated to wipe the liquid jetting section and thereby to clean it. (Item 14) The liquid jetting device described in Item 13, wherein the outer circumferential surface of the wiping member stated above moves relatively to the liquid jetting section in the course of wiping.
In the invention of Item 14, the liquid jetting section is wiped and cleaned when the outer circumferential surface of the wiping member moves relatively to the liquid jetting section. (Item 15) An invention of Item 15 for solving the problem is the liquid jetting device described in Item 14, wherein the speed of the aforesaid relative movement is 900 mm/s or less.
In the invention of Item 15, appropriate cleaning is conducted when the speed of relative movement is not more than 900 mm/s. (Item 16) The liquid jetting device described in either one of Item 13-Item 515 wherein the outside diameter of the wiping member is 5-50 mm and the inside diameter of the wiping member is 1-40 mm.
In the invention of Item 16, when using a wiping member whose outside diameter is 5-50 mm and inside diameter is 1-40 mm, an appropriate liquid-impregnating characteristic and wiping property can be materialized. (Item 17) The liquid jetting device described in either one of Item 13-Item 16, wherein the wiping member is made of a porous material having continuing air bubbles.
In the invention of Item 17, an appropriate liquid-impregnating characteristic and wiping property are materialized by a wiping member employing a porous material having continuing air bubbles. (Item 18) The liquid jetting device described in Item 17, wherein the porous material has its average porosity of 70% or more.
In the invention of Item 18, an appropriate liquid-impregnating characteristic or liquid-absorbing characteristic and wiping property are materialized when using a porous material having an average porosity of 70% or more. (Item 19) The liquid jetting device described in either Item 17 or Item 18, wherein the porous material has its average blow hole diameter of not more than 400 xcexcm.
In the invention of Item 19, an appropriate liquid-impregnating characteristic and wiping property are materialized when a porous material having an average blow hole diameter of not more than 400 xcexcm is used. (Item 20) The liquid jetting device described in either one of Item 13-Item 19, wherein the wiping means is provided with a fluctuating means which brings the wiping member into contact with the liquid jetting section and separates the wiping member from the liquid jetting section.
In the invention of Item 20, the fluctuating means brings the wiping member into contact with the liquid jetting section in the case of cleaning, and separates the wiping member from the liquid jetting section when cleaning is not conducted. (Item 21) The liquid jetting device described in either one of Item 12-Item 20, wherein the cleaning liquid supplying means supplies a cleaning liquid whose properties are similar to those of the liquid jetted by the liquid jetting section.
In the invention of Item 21, the influence of the cleaning liquid on a liquid jetted by the liquid jetting section is minimized by using a cleaning liquid whose properties are similar to those of a liquid jetted by the liquid jetting section. (Item 22) The liquid jetting device described in either one of Item 12-Item 21, wherein there is provided an impregnation amount adjusting means which adjusts an impregnation amount of the cleaning liquid in the wiping member by removing a part of the leaning liquid impregnated in the wiping member from the wiping member.
In the invention of Item 22, appropriate cleaning is realized by adjusting an impregnation amount of a cleaning liquid in the wiping member with the impregnation amount adjusting means. (Item 23) The liquid jetting device described in Item 22, wherein the impregnation amount adjusting means reduces an outside diameter of the wiping member partially.
In the invention of Item 23, a cleaning liquid in an appropriate amount is squeezed out when the impregnation amount adjusting means reduces an outside diameter of the wiping member partially. (Item 24) The liquid jetting device described in Item 23, wherein the impregnation amount adjusting means reduces a thickness of the wiping member by 50% of the thickness-0.5 mm.
In the invention of Item 24, an adjustment to an appropriate impregnation amount of a cleaning liquid can be materialized when the impregnation amount adjusting means reduces a thickness of the wiping member by 50% of the thickness-0.5 mm. (Item 25) The liquid jetting device described in either one of Item 22-Item 24, wherein the impregnation amount adjusting means is provided with a fluctuating means which brings the impregnation amount adjusting member into contact with the wiping member and separates the impregnation amount adjusting member from the wiping member.
In the invention of Item 25, the fluctuating means brings the impregnation amount adjusting member into contact with the wiping member in the case of cleaning, and separates the impregnation amount adjusting member from the wiping member when cleaning is not conducted. (Item 26) The liquid jetting device described in either one of Item 22-Item 25, wherein the wiping means wipes the liquid jetting section with its wiping member whose impregnation amount of the cleaning liquid has been adjusted by the impregnation amount adjusting means.
The invention of Item 26 makes it possible to clean the liquid jetting section appropriately by wiping the liquid jetting section with the wiping member impregnating the cleaning liquid which has been adjusted in terms of quantity. (Item 27) The liquid jetting device described in either one of Item 13-Item 26, wherein there is provided a cleaning liquid collecting means which collects the aforesaid cleaning liquid.
In the invention of Item 27, the collecting means collects an excessive or used cleaning liquid. (Item 28) The liquid jetting device described in either one of Item 13-Item 27, which is used for printing on a web.
In the invention of Structure 28, the liquid jetting device is used for printing on a web.